Frequency-tunable supercontinuum generation in photonic-crystal fibers by femtosecond pulses of an optical parametric amplifier

Supercontinuum emission is generated by the propagation of frequency-tunable femtosecond pulses of 1.1-1.5-Am radiation of an optical parametric amplifier through a photonic-crystal fiber. Nearly an octave's spectral broadening was observed when laser pulses with a duration of 80-100 fs and an energy of several nano-joules per pulse were coupled into a photonic-crystal fiber with a core radius of 1.5-3 mum. The spectral broadening of femtosecond pulses at 1.1-1.5 mum is shown to be much more efficient than the spectral broadening of femtosecond pulses of 800-nm Ti:sapphire laser radiation. The role of dispersion in spectral broadening and supercontinuum generation is discussed. In experiments on supercontinuum generation with an optical parametric amplifier, the influence of dispersion effects was reduced by decreasing the size of the fiber core, which allowed the efficiency of supercontinuum generation to be improved without increasing the laser intensity. (C) 2002 Optical Society of America.